Generally, high intensity discharge (HID) lamps require a higher starting voltage than is necessary for starting well-known fluorescent lamps. Also, one of the more popular techniques for activating HID lamps requires a starting element or probe positioned immediately adjacent a quartz arc tube located within a sealed outer envelope of the HID lamp. The arc tube also includes an electrode sealed into opposite ends thereof. An open circuit voltage is applied to the electrodes and to the starting probe causing the gap between the probe ano one of the electrodes to break down and emit electrons which are accelerated by the field between the lamp electrodes initiating a desired discharge between lamp electrodes.
Unfortunately, such techniques require removal of the probe from the active circuit in order to prevent premature lamp failure. Moreover, the end of the lamp having the starting probe therein tends to darken during the starting phase of the lamp which obviously reduces lamp efficiency. Moreover, other known starting schemes for lamps not having starting probes, "penning" gas mixtures and external thermal heating for example, tend to reduce the required starting voltage but unfortunately also adversely affect the lamp efficiency and life.
Additionally, U.S. Pat. No. 3,889,152 of Bodine Jr. et al and U.S. Pat. No. 3,976,910 of Owens et al suggest starting and operating circuitry for HID lamps wherein a transformer arrangement is employed. Therein, the transformer is connected to provide a potential greatly increased over the service potential and delayed by a triggering circuit such that a desired triggering potential occurs at the peak level of the AC voltage. However, transformers are not only undesirably heavy and cumbersome but also add greatly to the apparatus cost.
Further, a copending application bearing U.S. Ser. No. 431,956 filed Sept. 30, 1982 in the names of Stephen G. Johnson and William M. Labadini and assigned to the Assignee of the present application relates to a starting and operating circuit for a fluorescent lamp. Therein, a non-linear dielectric element is employed with a series connected resistor to effect a desired delay in a starting pulse potential. Although a fluorescent lamp having a starting voltage much lower than an HID lamp is employed, the resistor does serve to delay the desired starting pulse. However, the same resistor does expend energy which is very undesirable and also deleterious in so far as efficiency and costs are concerned.